The invention relates to electrorheological and magnetorheological valves.
Valves for electrorheological fluids are generally built of coaxial cylinder electrodes or of arrangements of parallel plates, between which the electrorheological fluid flows through. Due to an electric voltage applied to the electrodes, the viscosity of the electrorheological fluid located between the electrodes and therewith the through-flow resistance through the valve gap are controllable.
In comparison to conventionally controllable valves, electrorheological fluid valves are more simply constructed, because they include no moved mechanical parts such as closing or blocking bodies. A further advantage is that electrical signals can be directly transformed so that fast switching times can be realized with electrorheological fluid valves. Such valves are especially used in active shock absorbers and damping bearings, for example see U.S. Pat. Nos. 2,661,596, 4,880,216, EP 0,673,678 B1. In this context, active means that the damping behavior of such shock absorbers and bearings can be controlled by means of motion sensors on the basis of the instantaneously prevailing motion condition, by varying the electric field generated between the capacitor plates forming the valve gap.
Electrorheological fluids or magnetorheological fluids are fluids of which the rheological characteristics are controllable in a continuous or step-less manner via the electric or magnetic field. Generally, electrorheological fluids or magnetorheological fluids are suspensions, i.e. solid particles suspended in a carrier medium, which particles are polarizable by means of the electric or magnetic field. The reciprocal interaction between the electrode arrangement and the electrorheological fluid can be differentiated among three basic modes depending on the type of the fluid deformation, namely the shear mode (electrodes slide relative to one another in parallel planes), the flow mode (electrodes are rigidly or fixedly arranged and the fluid flows through between the electrodes), and the squeeze mode (electrodes vary their spacing distance relative to each other). These modes can also arise in combination. Further details in this context are found in the book xe2x80x9cTechnical Application of New Actuatorsxe2x80x9d(xe2x80x9cTechnischer Einsatz neuer Aktorenxe2x80x9d, published by Expert-Verlag, Renningen-Meinsheim, 1995, Chapter 3.2.1 and FIG. 3.1.
The object of the present invention is to provide a valve that utilizes the advantages of using electrorheological fluids and/or magnetorheological fluids as a hydraulic medium, that can be used in a variety of applications, and that can realize high pressures and through-flow rates. This object is achieved in that at least one bounding surface of the valve gap is embodied so as to be movable.
In the inventive valve, first the capacitor fields formed by the bounding surfaces are actuated or energized in such a manner that an electrorheological fluid flowing through the valve gap will become solidified in the valve gap and will close or block the valve gap. In this solidification, the solid particles orient themselves into chains. The solidified locations behave in the manner of elastic solid bodies. In order to increase the blocking pressure in the valve gap, a bounding surface of the valve gap is embodied to be movable according to the invention. The volume in the valve gap is thereby reduced, and as a result the electrorheological fluid is additionally transitioned into the squeeze mode. Between the solid particles that have oriented themselves into chains, electrostatic counterforces will now be effective due to the sliding displacement of the bounding surface or surfaces of the valve gap. In comparison to the flow mode acting by itself, therefore, a solidified electrorheological fluid plug acting as a blockage or closure in the combined flow mode and squeeze mode can build up a multiply higher pressure, before the fluid plug will be pushed further through the valve gap due to the pressure.
The above object of the invention can alternatively or additionally be achieved in that the electrorheological fluid flows through the valve gap in a meandering pattern or in a helical or spiral pattern. Due to the inventive configuration, a long valve gap can be achieved despite a small structural length of the overall valve, so that high pressures can be controlled by such a valve.